Control arrangements for vehicles are increasingly equipped with two computer elements especially for reasons of operational reliability and availability. This applies especially to the preferred area of application of the invention described below in combination with an electronic motor power control for motor vehicles. Examples of control arrangements of this kind are provided in U.S. Pat. No. 4,881,227 or the DE-A 35 39 407.
U.S. Pat. No. 4,881,227 describes a computer system with two processors in a motor vehicle wherein the two processors operate fully independently of each other and mutually monitor each other on the basis of different monitoring criteria, for example, based on a pregiven data exchange protocol and, in the case of a fault, the two processors can start each other. Suggestions with respect to a reliability concept for the application of such a computer system to an electronic motor power control are not described.
The DE-A 35 39 407 likewise describes a computer system having two processors for a motor vehicle. The suggestion is made that for normal operation work is allocated to the computers for improving the reliability and the speed of operation. This allocation of work provides that in a first processor, the determination of the desired value is made for a control; whereas, in the other second processor, the computation of the actuating variable takes place in dependence upon the difference between the desired value and the actual value. In this way, the computer speed as well as the speed of the control is increased by means of the distribution of the computer load. As a safety concept, it is further provided that all monitoring tasks which serve the operational reliability as well as the availability of the system are carried out by both processors parallel to each other in a redundant manner. Both computing elements have a scope of function at a high level with reference to the monitoring measures with a corresponding high complexity.